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Question: Answered & Verified by Expert
The magnifying power of a telescope with tube length 60 $\mathrm{cm}$ is 5 . Then the focal length of its eye piece is
PhysicsRay OpticsAP EAMCETAP EAMCET 2023 (15 May Shift 2)
Options:
  • A $20 \mathrm{~cm}$
  • B $40 \mathrm{~cm}$
  • C $30 \mathrm{~cm}$
  • D $10 \mathrm{~cm}$
Solution:
2371 Upvotes Verified Answer
The correct answer is: $10 \mathrm{~cm}$
The magnifying power of a telescope is given by
$\begin{aligned}
& m=\frac{f_0}{f_e}=5 \\
& f_0=5 f_e \\
& f_0+f_e=60 \mathrm{~cm} \Rightarrow 5 f_e+f_e=60 \\
& 6 f_e=60 \Rightarrow f_e=10 \mathrm{~cm}
\end{aligned}$
The focal length of its eye piece, $f_e=10 \mathrm{~cm}$

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